How can there be "self-regulation" on a platform that is "unstoppable, uncensorable, undeplatformable"?

I certainly agree that there are plenty of valuable forums that are not run by tech giants, but they function because they have dedicated moderation and censorship. The trouble is that the set of things I think people should be allowed to say is extremely large, but set of things I want to see in a forum or any sort of social media is much smaller. It doesn't have to be Jack Dorsey at the helm, but someone has to be sweeping up the filth to make a forum a place I want to interact with.